oncology
Unicameral Bone Cyst (Simple Bone Cyst)
intermediate
6 min
28 marks
6 questions
Clinical Scenario
A 10-year-old boy presents after falling during soccer and developing immediate left arm pain. He denies any previous symptoms. On examination, the upper arm is swollen and tender with limited shoulder movement. X-ray shows a well-defined lytic lesion in the proximal humerus metaphysis with a pathological fracture. A fragment of cortex has fallen to the bottom of the lesion.
AP radiograph of the proximal humerus demonstrating a unicameral bone cyst (simple bone cyst) complicated by a pathological fracture. The lesion presents as a centrally located, lytic metaphyseal defect with thinning of the overlying cortex. This image originates from a study on elastic intramedullary nailing for such lesions.
Source: Simple Bone Cyst Pathological Fracture • PMC2117015 • CC-BY
Questions
Question 1 (4 marks)
Describe the clinical and radiographic features of unicameral bone cyst.
Question 2 (5 marks)
What is the natural history and classification?
Question 3 (6 marks)
Describe the treatment options and their indications.
Question 4 (5 marks)
Compare unicameral bone cyst and aneurysmal bone cyst.
Question 5 (4 marks)
Discuss the management of pathological fracture through a UBC.
Question 6 (4 marks)
What are the outcomes and complications?
Exam Day Cheat Sheet
Must Mention
- •Age 5-15, male predominance
- •Proximal humerus 50%, proximal femur 25%
- •Central metaphyseal, well-defined
- •Fallen fragment sign = pathognomonic
- •Active (touches physis) vs latent
- •Steroid injection 80-90% success (2-3 injections)
Common Pitfalls
- •Confusing with ABC
- •Curettage before injection
- •Wrong success rates
- •Missing physis proximity
- •Not knowing fallen fragment
- •Wrong fracture management